During the processing of container blanks, paperboard sheets are successively passed through successive processing sections such as printing and die-cutting. Printing can have one, two, three or more printing sections and may employ one or more colored inks. Another section may include creasing. These various sections are rotationally (ie angularly) timed relative to each other so that each sheet theoretically passes through each section in register therewith. As the various operating members of the processing sections rotate in contact with successive sheets, each section is intended to perform an operation in the correct position on the sheet. In this way, all the operations get superimposed on top of each other on the sheet to form the final product, e.g. a printed container blank. Should any operation not be correctly positioned on the sheet, then the sheet is said to be out of registration, or out of register, with that operation, and this produces an inferior processed sheet.
The need to maintain accurate registration of paperboard sheets in the production of color printed container blanks has become more critical with higher production speeds and the demand for higher quality printing and multi-color graphics.